Ok so my daughter has a 110cc atv that ran perfectly until christmas morning when i gave it to her lol (good thing my sons worked so they rode that) the problem is it was really hard to start but that might have just been because it was cold but either way I got it going and took it up the street to get it warmed up. When I pulled into the driveway it died completely. I pulled it into the garage and checked the fuse which was blown. I put the spare fuse in it and it popped but I noticed that when i put it in right as it poped the brake light came on but the brakes were not applied. So I got a 15 amp fuse and put it in. I have figured out that with the key switch off it does not affect anything the fuse is fine but as soon as it is turned on the brake light comes on (no brakes applied) and if not shut off really quick the fuse will blow? Any ideas on where I should start the search? Thanks!

 

What brand quad? I just want to check and see if I have a wiring diagram.

It could be that your brake switch is stuck on and this has nothing to do with what's blowing the fuse. Or maybe it does... We'll find out.

The way to troubleshoot fuse blowing issues is to start unplugging stuff untill the fuse blowing stops. The look to see what the last thing you unplugged was, and dig in deeper right at the offending module.

But there are some other clues in your post. First, the fuse isn't blowing instantly. It takes a few seconds. What that means is that you don't have a direct short to ground. If you did the current from the battery would be enormous (like 100 amps). The fuse would go off like a flash bulb, and the fuse element inside would turn into a dark/silver metallic sheen on the inside of the fuse glass (I'm assuming you're using the tubular glass type).

Because the 15 amp fuse takes a few seconds to blow we can pretty much guestimate that the current going through the fuse is around 20 amps. Twenty amps at 12 volts is 240 watts of power (or about 1/3 of a horsepower if you want to think in mechanical equivalents). That should be making something *really* hot. Do you smell smoke when you do this? Does anything get noticably hot?

If your quad is dissipating 240 watts somewhere and nothing is getting hot that says that the thing dissipating that power has got to be mechanically big and thermally massive. That makes me think of the stator, or perhaps starter.

So now start unplugging stuff in the wiring harness until the fuse blowing stops. I would start by unplugging the voltage regulator. If a defective voltage regulator shorts across input to output, then the battery will discharge backwards through the battery charge winding in the stator to ground. That would draw a large amount of current and start heating up the stator inside the engine.

Resist the temptation to put an even larger fuse in. If you leave the ignition on you still are dissipating 240 watts. Something will be getting cooked, and it may not be the thing that is actually wrong. The shorted voltage regulator is a good example - the stator is the thing that will get cooked even though there was nothing wrong with it to begin with. The correct value fuse blowing protects the stator from overheating.